6 hours is ample time to ensure you are fine. What is his reasoning for you to need to stay one night? The only thing you will gain from it is a sore back... their beds are horrible! I think considering you are the one who is expected to do it his way, he needs to prove to you WHY - not the other way around.

Or

You could always avoid having to prove anything and go straight for the humorous smackdown.

"Sorry honey, but after giving birth to your child, I am going to need my bed more than your girlfriend is".